I have a 2014 GC Laredo and about four days ago I realized that my girlfriend in the passenger side wasn't wearing her seatbelt and both the beeping and the icon on the dash didn't show up. Since then it seems to not be working unless you tug on the seatbelt and you let it go. Sometimes even when I pull it over and click it and release it still no icon or beeping sound.
Btw I've done all of this you the GC on and in drive mode.

I had this problem and the dealer tried to tell me a person has to be sitting just right for it to register. I demanded they replace the sensor, after mentioning I would hate for something to happen and the seat belt didn't operate properly.